(1) Field of the Invention
This invention relates to an apparatus utilized for grounding a print circuit board of a liquid crystal display, and more particularly to an apparatus for forming an electric connection between the print circuit board and the metal box of the liquid crystal display.
(2) Description of Related Art
Along with enormous promotions of thin film transistor (TFT) fabrication technique, liquid crystal displays (LCD) are broadly adopted to personal digital assistants (PDA), notebooks (NB), digital cameras (DC), digital videos (DV), mobile phones, etc. Typically, a cold cathode fluorescent lamp (CCFL) is inserted into the LCD as a backlight source. A liquid crystal (LC) driving circuit is used to decode input signals for forming displaying data and scanning sequence data to further control the image of the LCD.
Ordinarily, in order to increase a display size of the LCD and to simplify the LCD fabrication sequence, the LC driving circuit is usually formed on a print circuit board (PCB) instead of formed traditionally on a glass substrate, accompanied by devices such as tape automated bounding (TAB), chip on glass (COG), chip on film (COF), etc. The PCB having the LC driving circuit is thus able to issue controlling signals to the LCD panel through a flexible flat cable (FFC).
Because environmental noises may disturb the LC driving circuit by messing the formation of the controlling signals, a proper electric shielding is usually introduced to the PCB so as to remove the charges left on the PCB during LC driving circuit operation. Definitely, upon such an arrangement, a specific grounding apparatus should be added on the PCB.
In FIG. 1, a typical LCD 10 comprises a metal cover 100, a plastic frame 200, an LCD panel 300, and a PCB 400. The LCD panel 300 and the PCB 400 are fixed on the opposite surfaces of the plastic frame 200 with an inter-connected FFC 410. The metal cover 100 boxes the plastic frame 200 therein to form an interior space for accommodating the LCD panel 300.
In order to prevent a particular electric current in the LC driving circuit from being disturbed by segregated charges on the PCB 400, as shown in FIG. 2, the PCB 400 has two grounding pins 430 formed on both edges 400b adjacent to sidewalls of the metal cover 100b for removing the segregated charges. Also referring to FIG. 1, each grounding pin 430 is fastened to the plastic frame 200 by using a PCB screw 435 and also electrically connected to the metal cover 100 by using an elastic conductive plate 440, which is fastened to the sidewall of the metal cover 100b by sending a grounding screw (not shown in this figure) into a hole 460 on the metal cover 100.
As mentioned, the grounding pin 430, the elastic conductive plate 440, the PCB screw 435, and the grounding screw are all used to achieve the purpose for grounding the PCB 400 in the art. Yet, with all these parts for grounding the PCB 400, a significant increase of time and labor on assembling an LCD is inevitable. In addition, while in screwing the PCB 400, the power to drive each screw should be carefully controlled so that screws as the fasten device won't damage the PCB 400 or the metal cover 100. Ordinarily, in order to control the screw driving power within a safety range, a power testing apparatus is also used in the assembling process to assure the process reliability.
Therefore, an improvement of a grounding apparatus targeting to minimize the number of elements and the assembling time without sacrificing the grounding effect is definitely welcome to the skilled persons in the art.